1. Field of the Invention
The present invention relates to the removal of subsurface contaminants and methods of using same, and more particularly, but not by way of limitation, the presently claimed and disclosed invention(s) relate to an integrated method for remediating subsurface contaminants through the use of a low concentration surfactant solution (and methods of making and using novel surfactant solutions) followed by an abiotic polishing process to thereafter achieve a substantially reduced subsurface contaminant concentration that surfactant flushing alone cannot achieve. Additionally, the surfactant solution alone can be used to achieve a substantially reduced subsurface contaminant concentration. Finally, the presently claimed and disclosed invention(s) include the use of a biodegradable co-solvent capable of substantially reducing subsurface contaminants having a viscosity of from 50-1500 cp and/or a low aqueous solubility.
2. Background Information Relating to the Invention
Surfactant enhanced subsurface remediation (SESR) is a unique technology for expediting subsurface remediation of non-aqueous phase liquids (NAPLs). Studies known to those in the art have previously evaluated the SESR technology in both laboratory scale studies and field scale demonstration studies. Traditionally, the surfactant system in SESR (typically an anionic or nonionic surfactant) is designed to remove organic contaminants (including chlorinated solvents) from contaminated soil. Surfactant systems significantly increase the solubility of hydrophobic organic compounds and, if properly designed and controlled, also significantly increase the mobility of NAPLs. A significantly reduced remediation time thereby results, as well as increased removal efficiency (up to 3 or 4 orders of magnitude) and reduced cost of NAPL removal through use of surfactant system for subsurface remediation.
Surfactant flushing solutions, typically, can be designed to be effective under most subsurface conditions. In most cases, the effectiveness of the surfactant flushing solutions is not reduced due to the presence of more than one contaminant. Naturally-occurring divalent cations and salts may affect the performance of certain surfactants, as well as the removal efficiency for cationic heavy metals. It is possible, however, to design an effective surfactant system for removal of the target contaminants under any of these conditions. A number of factors influence the overall performance and cost effectiveness of SESR systems. These factors include: local ground water chemistry; soil chemistry (e.g., sorption, precipitation); ability to deliver the surfactant solution to the area of contamination; surfactant effects on biodegradation of the NAPL compounds as well as degradation of the surfactants; public and regulatory acceptance; cost of the surfactant; recycle and reuse of the surfactant, if necessary; and treatment and disposal of waste streams. Bench scale tests (treatability studies) must be conducted on site specific soils and NAPL (if available) to ensure the optimal system is selected for a particular site.
Surfactant flushing can remove a large portion of the mass of subsurface contaminant liquid. In general, it is not expected that surfactant flushing alone will have a high probability of reducing the subsurface contaminant concentration to a level necessary to allow the site to be considered “remediated.” Therefore, a treatment train (or integrated) approach is necessary to speed up or achieve the closure of the site. It is to such an integrated approach involving a pre-selected surfactant solution flush coupled with an abiotic oxidation polishing step and methods thereof that the presently disclosed and claimed invention(s) is directed.
Typically, the viscosities of contaminants or NAPLs are between one to ten centipoises (cp, or 10−2 g cm−1sec−1) and, in some occasions, they may reach tens up to one hundred centipoises. Prior art (crude) oil recovery industries that used surfactant flushing for removal of highly viscous oils would generally apply a polymer solution (or so called “polymer drive”) in order to increase the sweep efficiency and oil recovery from the porous media and/or soils. Other generally known methods involve the addition of heat to reduce the oil viscosity, or the injection of foam in order to gain better mobility control to achieve higher oil recovery.
Such generally known methods are limited with respect to recovering significant amounts of complex viscous liquid contaminants, such as coal tars (commonly found at former manufactured gas plants), heating oils, bunker oils, creosotes (used as wood preservatives), polychlorinated biphenyls (PCBs), dioxins, and motor oils. Some of these complex waste oils might contain tens to hundreds of different compounds. Unfortunately, these complex wastes found at contaminated sites could also sometimes reach viscosities of from 50 to 1500 cp. In addition to these high viscosities, the low aqueous solubility of these complex organic fluids also poses a significant challenge for any attempt to remediate the impacted soil and groundwater.
Therefore, an improved surfactant flushing system is herein claimed and disclosed that is capable of substantially reducing the subsurface contamination of complex viscous NAPLs.